Compared to a higher carbohydrate diet, the OPTIFAST low-carbohydrate diet (43g/day) decreases hunger by inducing ketosis, which kickstarts the weight-loss process.
Before you start, it's important to understand typical ketosis symptoms. To avoid prolonging these, we recommend sticking to the program as prescribed. If you're concerned about any of your symptoms, or if they persist, speak to your doctor, nutritionist, or pharmacist and they can advise you on how to overcome or correct these before coming off the program.
Once your body is in ketosis, any excess ketones — water-soluble molecules produced by the liver during carbohydrate restrictive diets — that your body does not use for energy are excreted through your urine and breath. This is why some people experience bad breath during restrictive dieting, in some cases. You can measure your ketone levels in your urine using the Ketone Reagent Strips or Ketostix. Ketostix can be purchased over the counter from your local pharmacy.
Alternatively, your healthcare professional may test for ketones on your regular visits. Do not worry if you have a little bad breath while using OPTIFAST VLCD. This will only happen and last if you are in the Intensive Phase.
The amount of carbohydrates required to induce ketosis depends on a number of factors, and can actually vary from day to day depending on activity levels and fluid intake. A diet containing 50-70g of carbohydrates is generally considered low enough to produce ketones, but there is no absolute level that guarantees ketone production.
The OPTIFAST VLCD Program generally only produces a mild ketosis, which is why some people find that Ketostix do not show ketones, or the levels fluctuate. If you are losing weight steadily, then there is no need to be concerned.
1. Sumithran P, Proietto J. Ketogenic diets for weight loss: A review of their principles, safety and efficacy. Obes Res Clin Pract. 2008 Mar;2(1):I-II. doi:10.1016/j.orcp.2007.11.003. PubMed PMID: 24351673.